The present invention related generally to bus structures for electronic equipment and more particularly to an incremental bus structure for modular electronic equipment, such as measurement test instruments.
Typical electronic equipment buses, such as Compact PCI, VXI, VME and the like, have fixed bus structures that couple system wide buses and resources to various electronic modules in the electronic equipment. A typical instrument bus structure includes a number of electrically conductive lines incorporated into a mother board or backplane of the electronic equipment. Electrical connectors are electrically coupled in parallel to the bus lines with the connectors defining card or electronic module slots in the equipment. The bus structure includes lines defining address and data buses and lines for system wide resources, such as an audio bus, triggers, power supply voltages, reference clock, and the like. The electronic modules have electrical contacts that are electrically connected to the various electrical connectors. In a typical personal computer configuration, the electronic modules or cards may include a video processing and display card, a graphics accelerator card, I/O card, sound card, and the like. For measurement test equipment, the electronic modules or cards may include a central processing unit (CPU), video processing and display card, I/O card and various measurement signal generating, receiving and processing modules or cards. A characteristic of these types of bus structures is that the number of card or electronic module slots, as defined by the electrical connectors, is fixed by the manufacturer of the electronic equipment. This, in turn, defines the physical size of the instrument regardless of the number of modules or cards connected to the instrument bus.
Another type of measurement instrument uses an I/O bus to connect an electronic module or card to a system processor. The electronic module or card is usually a measurement specific card, such as an optical time domain reflectometer, metallic time domain reflectometer, or the like. Examples of such measurement test equipment having fixed bus structures are the model N1610A Service Advisor Portable Test Tablet, manufactured and sold by the Hewlett-Packard Company, Palo Alto, Calif., and the model FTB-300 UTD mainframe, manufactured and sold by EXFO Electro-Optical Engineering, Inc. Vanier, Quebec, Canada.
Both the N1610A and the FTB-300 UTD are base platforms that receive the measurement specific modules. Both platforms have a front panel display output, basic front panel controls, a controller operating under control of Window-based software, and a specified number of measurement module slots. The N1610A has two module slots that accept either two single wide plug-in modules or one dual width plug-in module. The FTB-300 UTD has three module slots that accept up to three single slot modules or a three slot wide single module. The fixed number of slots in these instruments do not allow for expanding the number of modules in the instrument without redesigning the instrument.
Another type of bus is the Universal Serial Bus (USB) bus that has a host controller and one or more hubs. The USB bus is a four line bus for power, ground and a bi-directional differential communications. The USB bus is connected from the controller to a first hub via a four wire USB cable connected to respective USB connectors. The hub may have multiple outputs that allow connections to other devices. The controller talks to the hub and dynamically assigns addresses for each hub output. Additional hubs connected to the first hub will dynamically assigned addresses by the controller. The controller communicates with a system processor, such as a PENTIUM(copyright) microprocessor, while the hub outputs may be coupled to digital signal processors that acquire and process measurement data. While the USB bus allows for connecting a large number of device to the bus, it has the drawback of a high software overhead to control the dynamic addressing of the hub outputs and the flow of data over the communications line. Additionally, the USB bus requires specific USB controller and USB hub chip sets. Further, all communications over the bus has to pass through the USB bus controller.
What is needed is a bus structure that is not limited to a predefined number of slots, as defined by electrical connectors on a mother board, back plane or I/O interfaces. The bus structure should be expandable to accept any number of cards or modules but not encumbered by high software overhead or the need for specialized chip sets. The bus structure should also connect directly to system controller and not restricted to an intermediate controller.
Accordingly, the present invention is an incremental bus structure that includes a system bus having a plurality of electrically conductive lines and at least a first incremental bus structure element. In the preferred embodiment of the invention, the bus structure is implemented using at least one bus structure element in a modular measurement instrument that includes a base unit and one or more measurement modules. The incremental bus structure provides system bus resources to and from the base unit and measurement modules via the incremental bus structure elements. The incremental bus structure element includes an interface connector having at least first and second electrically conductive input contacts and first and second electrically conductive output contacts with the second input contact connected to the first output contact. A first of the system bus electrically conductive lines is coupled through the first input contact of a first interface connector to a first electronic element and a second of the electrically conductive lines is coupled through the second input contact to the first output contact.
The bus structure element is preferably constructed with an input interface connector having the first and second electrically conductive input contacts and an output interface connector having the first and second electrically conductive output contacts. A flexible substrate having at least first and second electrically conductive lines formed thereon connects the input and output interface connectors together. Respective ends on one side of the first and second electrically conductive lines are electrically connected to the respective first and second electrically conductive input contacts of the input interface connector. The other end of the first electrically conductive line is coupled to an electronic element and the other end of the second electrically conductive line is connected to the first electrically conductive output contacts of the output interface connector.
The incremental bus structure is expandable to include a second interface connector having at least first and second input contacts and first and second output contacts with the first and second output contacts of the first interface connector electrically coupled to the first and second input contacts of the second interface connector. The second input contact of the second interface connector is connected to the first output contact of the second interface connector. The second electrically conductive line of the system bus is coupled through the first input contact of the second interface connector to a second electronic element. Various types of electrical signals, such as address signals, clock signals, request service signal, and power-on signals, may be passed on to the first and second electronic elements via the first and second electrically conductive lines of the bus structure. The electronic elements may include controllers, power supplies and the like
The incremental bus structure is implemented in a modular measurement instrument that includes a base unit having an instrument bus consisting of electrically conductive lines that are electrically coupled to corresponding electrically conductive contacts of an instrument bus interface connector. In the preferred embodiment of the invention, the instrument bus has at least one subset of N electrically conductive lines. At least a first measurement module having an interface connector containing input and output electrically conductive contacts is plugged into the base unit with the input electrically conductive contacts of the first measurement module interface connector being electrically coupled to the electrically conductive contacts of the instrument bus interface connector. The measurement module interface connector has at least one subset of N input and output electrically conductive contacts corresponding with the subset of N electrically conductive lines. The first input electrically conductive contact of the subset is electrically coupled to electronic elements in the measurement module and the second and remaining input electrically conductive contacts of the subset are offset and electrically coupled to the first and subsequent output electrically conductive contacts of the subset.
The bus structure in the modular measurement instrument may further include a plurality of subsets of N electrically conductive lines with the measurement module interface connector having corresponding sets of N input and output electrically conductive contacts. The first input electrically conductive contact of each subset in the measurement module interface connector is electrically coupled to the electronic elements in the measurement module and the second and remaining input electrically conductive contacts of each subset in the measurement module interface connector are offset and electrically coupled to the first and subsequent output electrically conductive contacts of each subset.
The modular measurement instrument may include additional measurement modules with each module having an interface connector containing input and output electrically conductive contacts. The input electrically conductive contacts of each of the additional measurement module interface connectors are electrically coupled to the output electrically conductive contacts of another of the measurement module interface connectors. Each of the measurement module interface connectors has at least one subset of N input and output electrically conductive contacts corresponding with the subset of N electrically conductive lines. The first input electrically conductive contact of the subset for each measurement module interface connector is electrically coupled to the electronic elements in the corresponding measurement module and the second and remaining input electrically conductive contacts of the subset are offset and electrically coupled to the first and subsequent output electrically conductive contacts of the subset. The instrument bus may also be implemented with a plurality of subsets of N electrically conductive lines in a modular measurement instrument with additional measurement modules. Each of the additional measurement module interface connectors have corresponding subsets of N input and output electrically conductive contacts. The first input electrically conductive contact of each subset in each of the measurement module interface connectors is electrically coupled to the electronic elements of the corresponding measurement module and the second and remaining input electrically conductive contacts of each subset in each of the measurement module interface connectors are offset and electrically coupled to the first and subsequent output electrically conductive contacts of each subset.
Where the incremental bus structure has a plurality of subsets of N electrically conductive lines, the bus structure elements in the form of the measurement module interface connectors has corresponding plurality of subsets of N input and output electrically conductive contacts. The flexible substrate also includes the electrically conductive lines having a plurality of subsets of N electrically conductive lines corresponding to the subsets of N electrically conductive lines of the instrument bus. The first ends of the subsets of N electrically conductive lines are electrically connected to the corresponding electrically conductive input contacts of the input interface connector. The other ends of each of the first electrically conductive lines of each of the plurality of subsets of N electrically conductive lines are coupled to the electronic elements of the corresponding measurement module and the other ends of the second and subsequent electrically conductive lines of each of the plurality of N electrically conductive lines are offset and connected to the first and subsequent electrically conductive output contacts of the output interface connector.